THE INDUCTION OF LACTATION DURING PREGNANCY IN RABBITS AND THE SPECIFICITY OF THE LACTOGENIC HORMONE

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Abstract
A localized lactation was induced in pregnant and pseudo-pregnant rabbits by injecting small dosages of lactogenic hormone directly into the teats. Nine of 10 rabbits injected beginning on the 15th day of pregnancy came into lactation, usually by the 18th day, without disturbing the pregnant state. Only 2 of 7 rabbits injected on the 10th day of pregnancy were induced to lactate by the 15th day without terminating pregnancy. Fourteen pseudopregnant rabbits appeared to respond like pregnancy rabbits when given the same amt. of hormone. In another expt., attempts were made to determine whether hormones other than lactogen could induce localized lactation in pseudopregnant rabbits. Three rabbits received single injns. into 5 nipples of each of the following hormones lactogen, whole pituitary extract, thyrotrophin, thyroxine and adrenal cortical hormone. Only the mammary sectors which received lactogen and whole pituitary extract came into lactation. This is believed to show that only lactogen has the specific property of acting directly on the mammary epithelium to induce lactation.